sbomify Insights

Search by CVE or GitHub advisory id, package name or title.

CVE-2026-12985 Mattermost DCR redirect URI allowlist bypass via improper URL component validation

Medium 6.8 Published Updated

Attackers can bypass OAuth redirect URI allowlists to steal authorization codes, potentially leading to account takeover.

Exploited in the wild
Not known
Login needed
Not needed
Attackable
Over the internet
Victim action needed
A user has to click or open something
Fix
None listed

What is CVE-2026-12985?

CVE-2026-12985 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 14 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 Mattermost failed to validate Dynamic Client Registration redirect URIs by URL component (matching glob patterns against the raw URI string instead) which allows a remote unauthenticated attacker to register an OAuth client with an attacker-controlled callback host that bypasses the configured redirect URI allowlist via a crafted redirect URI that places an allowlisted host/path suffix inside the query string.. Mattermost Advisory ID: MMSA-2026-00700

Weakness: CWE-601

Which versions are affected by CVE-2026-12985?

It affects 1 product.

Products include Mattermost Mattermost Server.

How do I fix CVE-2026-12985?

No fix has been published for CVE-2026-12985 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-12985 being exploited?

There is no known exploitation of CVE-2026-12985 in the wild and no public exploit code.

All Mattermost Mattermost Server vulnerabilities

Sources

Also known as GHSA-c92j-r2f4-67xg.

Is CVE-2026-12985 in your software?

Upload an SBOM and sbomify checks it against every vulnerability here, every day.

Check your SBOMs for free